In mobile communication system such as, for example, GSM, WCDMA or TD-SCDMA, there is a unique number for each user, which is used to distinguish between the different users within the system. This number is usually a number for a mobile telephone or a similar device in the system.
However, there is now a growing demand from mobile users to use more than one number in parallel; it may, for example, be desirable to be able to be reached via one number for business calls, via another number for private calls and via yet another number for family purposes, etc.
There are some more or less obvious solutions for these requirements, such as, for example, carrying around more than one mobile phone or exchanging SIM (Subscriber Identity Module) cards in one and the same telephone or terminal. All of these solutions are obviously quite inconvenient for a user.